JPH0998581A - Inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To feed a load with a single phase three wire AC power in self-contained operation without modifying the system configuration. SOLUTION: The inverter comprises semiconductor switch groups 1, 2, 3, 4 connected into a single phase bridge for converting a DC source power 14 inputted through a parallel capacitor 15 into a single phase two wire AC power. AC power is fed to a load 6 by performing interlinked operation with a single phase three wire power system through an AC filter comprising a reactor 12 and a parallel capacitor 13 provided in the output circuit of inverter, a switch 9, and a single phase transformer 10 having a secondary neutral connected with a switch 8. When the operation is interlinked with power system, the switch connected with the secondary neutral of single phase transformer 10 is turned off and when self-contained operation is performed, the switch 8 is turned on to feed a single phase three wire AC power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device which can be connected to a single-phase, three-wire type power system and can be supplied with a single-phase, three-wire type AC power in a self-sustaining operation.

[0002]

2. Description of the Related Art The circuit configuration of an inverter device that operates in conjunction with a single-phase three-wire power system is shown in the block diagram of FIG. In FIG. 2, an inverter including a group of semiconductor switches 101, 102, 103, 104 connected in a single-phase bridge receives DC power supplies 115 and 116 in series via parallel capacitors 117 and 118, and a reactor 111 provided in an output circuit. And 112 and parallel capacitor 113
And outputs a single-phase three-wire type AC power through an AC filter consisting of The inverter is connected to the power system of the single-phase three-wire system via the changeover switches 107 and 108,
AC power is supplied to the load 106.

[0003]

When the U-phase and the V-phase are unbalanced on the side of the power system connected to the inverter, the output current of the inverter is corrected for each phase so as to correct this unbalance. Need to control. For this reason, current detectors 109 and 110 are provided in the U-phase and V-phase in the output circuit of the inverter, and these detection signals are fed back to the control circuit 105 of the inverter, and the semiconductor switch group 101, which constitutes the inverter, 102, 103, 10
Control 4 That is, not only is the circuit configuration of the conventional inverter that is interconnected with the single-phase three-wire power system complicated, but the inverter is controlled based on two current detection signals, so the control circuit is also complicated. The control method was not easy. The present invention has been made in order to solve the above-mentioned drawbacks of the conventional inverter, and provides an inverter device capable of interconnected operation with a single-phase three-wire power system equipped with a simple circuit configuration and control method. It is the one we are trying to provide.

[0004]

The present invention is an inverter device comprising a group of semiconductor switches in a single-phase bridge connection for converting DC power input via a parallel capacitor into AC power of a single-phase two-wire system. The inverter device is connected to a single-phase three-wire power system via an AC filter provided in the output circuit of the inverter device and a single-phase transformer provided with a changeover switch at the secondary side neutral point, and In the case of interconnected operation, the changeover switch provided at the secondary side neutral point of the single-phase transformer is turned off, and then AC power is supplied to the load via the single-phase transformer to separate it from the power system. In case of self-sustaining operation, 2 of the single-phase transformer
A single-phase, three-wire type AC power is supplied to the load after turning on the changeover switch provided at the secondary neutral point.

[0005]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a circuit configuration of an inverter device according to the invention. The inverter device including the semiconductor switch groups 1, 2, 3, and 4 connected in a single-phase bridge is supplied with the DC power supply 14 through the parallel capacitor 15, and the reactor 12 is provided in the output circuit of the inverter device.
And a single-phase two-wire type AC power is output through an AC filter including the parallel capacitor 13. A single-phase three-wire type load 6 is connected to the secondary side of a single-phase transformer 10 provided with a changeover switch 8 at the secondary side neutral point, and further, a single-phase three-wire type load 6 is connected via a changeover switch 7. It is connected to the power grid. When the changeover switch 9 provided on the primary side of the single-phase transformer 10 is turned on, the inverter device passes through the single-phase transformer 10 and the single-phase three-wire power system and load 6
Connected to. A current detector 11 is provided in the output circuit of the inverter device, and this detection signal is sent to the control circuit 5
Is fed back to control the inverter device.

When the inverter device is connected to the single-phase three-wire type power system, the changeover switch 8 provided at the secondary side neutral point of the single-phase transformer 10 is turned off, and then the changeover switch 9 is used. Is turned on to connect the inverter device to the primary side of the single-phase transformer 10, and the interconnection operation with the power system is performed via the single-phase transformer 10. Even if the U-phase and V-phase on the power system side are unbalanced, the inverter device uses the single-phase transformer 10
Since it is connected to the power system via the power supply system, balanced single-phase two-wire AC power is supplied to the system side without being affected by the system side. Therefore, the control method is also simple. Further, in the case of performing the self-sustained operation separately from the power system, the changeover switch 8 provided at the secondary side neutral point of the single-phase transformer 10 is turned on and then provided on the primary side of the single-phase transformer 10. A certain changeover switch 9 is turned on, and the inverter device is connected to the power system via the single-phase transformer 10. Next, when the changeover switch 7 provided between the load 6 and the electric power system is turned off, the inverter device is disconnected from the electric power system, and the load device 6 operates independently and supplies single-phase three-wire AC power to the load 6 alone. To do.

[0007]

As described above, the inverter device according to the present invention is a single-phase two-wire type AC power generating inverter. However, a single-phase transformer having a changeover switch at the secondary side neutral point is used. By connecting to the power system via the power supply system, single-phase three-wire AC power can be supplied to the load during independent operation without major system configuration changes, and it is not affected by the unbalance of the connected power system. It can supply stable AC power.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an inverter device of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of an inverter device according to a conventional technique.

[Explanation of symbols]

 1, 2, 3, 4 Semiconductor switch 5 Control device 6 Load 7, 8, 9 Changeover switch 10 Single-phase transformer 11 Current transformer 12 Reactor 13, 15 Parallel capacitor 14 DC power supply

Claims (1)

[Claims] 1. An inverter device comprising a group of semiconductor switches in a single-phase bridge connection for converting direct-current power input via a parallel capacitor into single-phase two-wire alternating-current power, the inverter device being provided in an output circuit of the inverter device. The inverter device is connected to a single-phase three-wire type power system through an AC filter and a single-phase transformer provided with a changeover switch at the neutral point on the secondary side, and is interconnected with the single-phase three-wire type power system. In this case, the changeover switch provided at the secondary side neutral point of the single-phase transformer is turned off, and then the single-phase two-wire type AC power is supplied to the load through the single-phase transformer, and the power system In the case of further independent operation, the changeover switch provided at the secondary side neutral point of the single-phase transformer is turned on, and single-phase three-wire type AC power is supplied to the load. Inverter Location.